Infinitives are two words that combine to form a single verb, such as “to walk,” “to draw” and “to swim.” Although the pair of words is treated like one verb, “to” is actually a particle; the verb itself is the infinitive. When “to” is dropped, the infinitive is called a “zero (or bare) infinitive.” The recipe for an infinitive is “to” followed by the verb’s simple form.
Infinitives in Use
“Marge wanted to walk to the store.”
“For dinner, Benny decided to broil some steaks.”
“The dog across the street began to bark.”
When a word, usually an adverb, is placed in the middle of an infinitive, the infinitive has been “split.” There has been a controversy over this habit since the 1800s, and the man who is said to have started the argument insisted that the two parts are inseparable, treating the “to” as more than just a prepositional marker. The two words are treated as one verb but are not inseparable, so split infinitives are not illegal according to the rules of English grammar.
Since the argument has not completely died, many still fuss over splitting infinitives. In formal and academic writing, it might be wise to avoid it, simply keep from attracting attention to the writing instead of the topic, unless the result is clumsy or sounds strange to the ear.
As an example, the sentences below have had their infinitives split.
“Marge wanted to quickly walk to the store.”
“For dinner, Benny decided to swiftly broil some steaks.”
“The dog across the street began to loudly bark.”